A treatise on the Holy Spirit, Biblical references to the Trinity, Baptism, and the relation of all this to Christ's Church.
St. Basil the Great was the brother of St. Macrina and St. Gregory of Nyssa, and a great friend of St. Gregory Nazianzen. He served as Bishop of Caesarea, where he built the Ptochoptopheion, a huge complex of buildings to serve as a hotel for friendless strangers, a hospital and clinic for the poor, and vocational training for unskilled workers. He wrote this treatise for Nazianzen's cousin Amphilochius, as a reply to a new movement denying the divinity of the Holy Spirit.